Neon, a serverless Postgres system, has introduced a new persistent data structure that significantly enhances the speed of their Write-Ahead Log (WAL) indexing, achieving a 70 to 2000x speedup compared to previous methods. The system separates storage from compute and offers features like usage-based billing, autoscaling, and database branching. The challenge addressed is efficiently finding the WAL for a given data point, a problem previously tackled with various data structures, including R-Trees and segment trees, which proved inadequate. The innovative solution utilizes Rust Persistent Data Structures (RPDS), which allow querying past states efficiently by making tree-based data structures immutable through a copy-on-write method. This approach not only accelerates the search process but also keeps the complexity within manageable bounds, highlighting the potential of persistent data structures in high-performance computing scenarios.